Biomagnetic therapy is an alternative form of medicine which utilizes magnetic fields to treat disease. Although known to the ancient Greeks, it has never achieved mainstream status in western medicine. Nevertheless, over the years there have been persistent accounts in the lay press, as well as numerous case and controlled studies in modern peer-reviewed medical journals suggesting the effectiveness of magnetic fields to treat a multitude of ailments. Unfortunately, taken as a whole, with exceptions of the use of pulsed magnetic fields to promote healing of non-union bone fractures, and in transcranial magnetic stimulation as a treatment of psychiatric disorders, these reports are generally unconvincing. A major problem is that there has never been a universally acceptable theoretical framework to explain how magnetic fields might interact with living tissue to account for all of the diverse therapeutic benefits attributed to them. Recently we have established a mechanism, and demonstrated in a reproducible manner in real time, how polarized and motile immune cells are sensitive to very weak approximately 0.0001 volts/meter) ultra-low frequency (approximately 0.1-0.05 Hz) pulsed electric fields. We have also demonstrated that weak magnetic fields can be utilized to induce such electric fields. Furthermore, we have shown in vitro that magnetically induced pulsed electric fields can deactivate inflammatory immune cells, suggesting a rational method as to how biomagnetic therapy can be utilized in the treatment of inflammatory disease. Thus in this proposal it is our objective to extend our in vitro findings, to the in vivo arena in an animal model system. In particular we will critically test whether ultra- ow frequency pulsed magnetic fields of the kind that are effective in vitro, can deactivate inflammatory immune cells in a mouse collagen induced arthritis model. It is our long term goal to put biomagnetic therapy on a sound evidence based physiological foundation, and to translate our preliminary work so that biomagnetic therapy of human inflammatory disease can become an integral part of contemporary medical practice.